Axially cooled airfoil

ABSTRACT

An airfoil is provided. The airfoil includes an airfoil blade. The airfoil blade has a trailing edge, a pressure sidewall and a suction sidewall, where a portion of the airfoil blade has a widest cross section when measured between the suction sidewall and the pressure sidewall. A plenum is located along the widest cross section. At least one passageway extends in an axial direction from the plenum and terminates at the trailing edge. The at least one passageway is in fluid communication with and receives a flow from the plenum.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to an airfoil, and morespecifically to an airfoil having at least one passageway extending inan axial direction from a plenum and terminating at a trailing edge.

Turbine engines include rotor blades that extend radially outwardly froma turbine rotor. The rotor blades include a shank and an airfoil. Hotgasses usually travel through a series of internal cooling passages orholes that are located within the airfoil. The cooling holes in theairfoil are typically oriented in a radial direction.

Orienting the cooling holes in the radial direction may create severalconcerns. For example, radially oriented coolant channels usually havewarmer coolant located near the tip of the airfoil. Thus, tip damage dueto overheating may occur. Radially oriented cooling holes also tend toprovide less cooling at a leading edge of the airfoil, where heat loadis typically high. Moreover, because the turbine rotor rotates duringoperation, cooling of the airfoil can become complex. This is becausethe rotary forces that are exerted on the airfoil as the turbine rotoroperates are generally perpendicular to the orientation of the radiallyoriented cooling holes. This difference may lead to uneven cooling ofthe airfoil. Coriolis forces also act upon the airfoil and maynegatively affect the cooling as well. The Coriolis force isproportional to the vector product of the velocity vector of the coolantflowing through the cooling holes and the angular velocity vector of therotating airfoil. Thus, the Coriolis forces act upon the coolant locatedin the radially oriented cooling holes in a tangential direction. Thisredistributes coolant in the presence of Coriolis force, which resultsin non-uniform heat transfer of the airfoil.

One approach to improve airfoil cooling involves increasing the coolingflow by bleeding off more engine compressor air. However, this approachaffects the efficiency of the turbine. Therefore, it would be desirableto provide an airfoil having an effective cooling system that wouldreduce the adverse effect of rotational and Coriolis forces.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, an airfoil is provided. Theairfoil includes an airfoil blade. The airfoil blade has a trailingedge, a pressure sidewall and a suction sidewall, where a portion of theairfoil blade has a widest cross section when measured between thesuction sidewall and the pressure sidewall. A plenum is located at thewidest section of the airfoil. At least one passageway extends in anaxial direction from the plenum and terminates at the trailing edge. Atleast one passageway is in fluid communication with and receives a flowfrom the plenum.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is an illustration of an exemplary airfoil having an airfoilblade;

FIG. 2 is a top view of the airfoil shown in FIG. 1;

FIG. 3 is an illustration of an alternative embodiment of the airfoilshown in FIG. 1;

FIG. 4 is an illustration of another alternative embodiment of theairfoil shown in FIG. 1;

FIG. 5 is a turbulated cooling passageway of the airfoil shown in FIG.1;

FIG. 6 is an illustration of yet another alternative embodiment of theairfoil shown in FIG. 1;

FIG. 7 is an illustration of another alternative embodiment of theairfoil shown in FIG. 1; and

FIG. 8 is an illustration of yet another alternative embodiment of theairfoil shown in FIG. 1.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is an illustration of an exemplary airfoil indicated by referencenumber 10. In one embodiment, the airfoil 10 is employed in a rotor of aturbine engine (not shown). The airfoil 10 includes an airfoil blade 20and a platform 24. The airfoil blade 20 projects outwardly from theplatform 24. The airfoil blade 20 is attached or coupled to the platform24 at a hub or root 28. The airfoil blade 20 extends outwardly andterminates at a tip portion 30. The airfoil blade 20 includes a leadingedge 32 and a trailing edge 34, as well as a pressure sidewall 40 and asuction sidewall 38. A plenum 36 is located within the airfoil blade 20and is shown in phantom line. In the exemplary embodiment as shown, theplenum 36 is located at the leading edge 30 of the airfoil blade 20, andmay extend along a length of the airfoil blade 20 from the root 28 tothe tip portion 30. However, it is understood that the plenum 36 may belocated in other locations of the airfoil blade 20 as well.Specifically, in an alternative embodiment, the plenum 36 may be locatedat an area of the airfoil blade 20 having the widest cross section whenviewed from the tip portion 30. Specifically, referring to FIG. 2, anarea A is denoted at the tip portion 30, and represents the portion ofthe airfoil blade 20 having the widest cross section when measuredbetween the suction sidewall 38 and the pressure sidewall 40.

The plenum 36 is fluidly connected to and in communication with at leastone cooling passageway 42. The cooling passageways 42 extend axiallyfrom the plenum 36 and terminate at the trailing edge 34 as a series ofcooling holes 50. In the embodiment as shown in FIG. 1, a plurality ofcooling passageways 42 are located between the root 28 and the tipportion 30 for providing cooling to the airfoil blade 20.

The plenum 36 is positioned to receive a cooling flow 52 through anaperture 54 located at the root 28 of the airfoil blade 20. The coolingflow 52 travels through the plenum 36 and to the cooling passageways 42.A portion of the cooling flow 52 may exit the airfoil blade 20 throughan aperture 56 located at the tip portion 30. The remaining amount ofthe cooling flow 52 exits the cooling passageways 42 through theapertures 50 located at the trailing edge 34 of the airfoil blade 20.

In the exemplary embodiment as shown, the airfoil blade 20 includes agenerally angled outer profile P. The cooling passageways 42 may alsoinclude a generally curved profile for accommodating the generallyangled outer profile P of the airfoil blade 20. Turning now to FIG. 2, atop view of the airfoil blade 20 viewed from the tip portion 30 isillustrated. Referring now to both of FIGS. 1-2, the cooling passageways42 include a generally acruate or curved profile extending from theplenum 36 to the trailing edge 32. The generally curved profile of thecooling passageways 42 typically correspond with at least a portion ofthe generally angled outer profile P of the airfoil blade 20. Thegenerally curved profile of the cooling passageways 42 may bemanufactured using a variety of approaches. In one exemplary embodiment,the cooling passageways 42 are manufactured using a Shaped TubeElectrochemical Machining (STEM) process that facilitates a curveddrilling process. However it is understood that other approaches may beused as well for creating the cooling passageways 42.

Conventional airfoil blades that are currently available typically havecooling holes oriented in the radial direction. Radially orientedcoolant channels usually have warmer coolant located near the tip of theairfoil. Thus, tip damage due to overheating can occur. The coolingpassageways 42 are oriented in the axial direction, which provides formore uniform cooling flow at the tip portion 30 of the airfoil blade 20.Moreover, the airfoil blade 20 may also provide increased cooling at theleading edge 32 when compared to a conventional airfoil blade havingradially oriented cooling holes.

Rotary forces are exerted during operation of the turbine engine (notshown), which may lead to uneven cooling of conventional airfoil bladesthat have radially oriented cooling holes. Coriolis and rotationalbuoyancy forces also act upon the coolant located in the cooling holesin tangential and radial directions. Radially oriented cooling holes areperpendicular to the direction in which the Coriolis forces act. Incontrast, the cooling passageways 42 of the airfoil blade 20 areoriented in the axial direction that is generally parallel to thedirection of rotation of the turbine engine. Therefore, adverse effectsdue to rotational and Coriolis forces may be reduced or substantiallyprevented in the airfoil blade 20 when compared to a conventionalairfoil blade having radially oriented cooling holes.

FIG. 3 is an alternative embodiment of an airfoil blade 120. In theembodiment as shown, at least one cooling passageway 180 terminates at atip portion 130 of the airfoil blade 120, while the remainingpassageways 142 terminate at a leading edge 132 of the airfoil blade120. That is, the cooling passageways 180 are generally oriented in partin a radial direction of the airfoil blade 120. Part of the coolingpassageways may be in radial orientation of the airfoil blade 120because it is desirable to have radial exit in the tip portion 130.

FIG. 4 is another alternative embodiment of an airfoil blade 220. In theembodiment as shown, the cooling passageways 242 are not generallyradially aligned with one another and instead have a staggeredconfiguration with respect to one another. Staggering the coolingpassageways 242 may reduce the centrifugal tension that is exerted onthe airfoil blade 220. FIG. 4 also illustrates the cooling passageways242 having a tapered configuration, where the diameter of the coolingpassageways 242 generally decrease as the cooling passageways 242approach a trailing edge 232 of the airfoil blade 220. That is, a firstdiameter D1 of the cooling passageway 242, which is measured at aproximate end of the cooling passageway 242 with respect to a plenum236, is greater than a second diameter D2. The second diameter D2 ismeasured at a distal end of the cooling passageway 242 with respect tothe plenum 236. Turning now to FIG. 5, an enlarged view of a portion ofone of the cooling passageways 242 is shown. The cooling passageway 242includes a plurality of protrusions 284 which act as turbulators. Thatis, the protrusions 284 may create turbulence in the coolant flow 252that exits the cooling passageway 242.

In yet another embodiment, which is shown in FIG. 6 an airfoil blade 320is shown having a number of cooling passageways 342 with varyingdiameters. The cooling passageways 342 also include differentconfigurations. That is, a portion of the cooling passageways 342 have afirst configuration where a first diameter D1′ of the cooling passageway388, which is measured at a proximate end of the cooling passageway 342with respect to a plenum 336, is greater than a second diameter D2′. Thesecond diameter D2′ is measured at a distal end of the coolingpassageway 342 with respect to the plenum 336. The cooling passageways388 have a stepped configuration. That is, the change in diameterbetween the first diameter D1′ and the second diameter D2′ does notchange gradually, but rather changed by a step 398 that is located inthe cooling passageways 388. The remaining cooling passageways 390 alsohave a stepped configuration as well, and include a step 399. The firstdiameter D1′ is less than the second diameter D2′ in the remainingcooling passageways 390. This configuration may be used in an effort toenhance regional cooling of the airfoil blade 320. This arrangement mayalso be used for increasing the effectiveness of thermal management.This is because an increased diameter of a cooling passageway has slowercoolant velocity, and thus results in a lower heat transfer coefficient.Therefore, the coolant located within this type of cooling passagewayincludes a cooling potential that may be preserved for locations thatare located downstream in the cooling passageway.

In another embodiment of an airfoil 420, which is shown in FIG. 7, thecooling passageways 442 are arranged in a diagonal configuration. Thatis, at least one of the cooling passageways 442 is oriented to extendaxially and crosses over another one of the cooling passageways 442.Specifically, at least one of the cooling passageways denoted byreference number 492 has a base portion 494 that is situated proximateto a plenum 436. The base portion 494 is situated below a base portion496 of another cooling passageway that is denoted by reference number498. The cooling passageway 492 extends axially in a direction towards atip portion 430 of the airfoil blade 420, thereby crossing the othercooling passageway 498. The other cooling passageway 498 extends axiallyin a direction away from the tip portion 430 of the turbine airfoil 420.Thus, the cooling passageway 492 is oriented to extend axially andcrosses the cooling passageway 498. In the embodiment as shown, aportion of the cooling passageways 442 also terminate at the tip portion430 of the airfoil blade 420, while the remaining cooling passageways492, 498 terminate at a leading edge 432 of the airfoil blade 120.Having at least a portion of the cooling passageways 442 arranged in thediagonal configuration as shown in FIG. 7 may generally prevent hotspots in the airfoil blade 420. Specifically, in the event a hot streakis present, the diagonal configuration may substantially reduce orsubstantially prevent hot spots on the airfoil blade 420. In otherwords, the diagonal configuration of the cooling passageways 442 do notgenerally follow hot-gas path streamlines if there are relatively strongtemperature gradients across streamlines.

In yet another embodiment of an airfoil blade 520, which is shown inFIG. 8, the airfoil 520 includes a serpentine passageway 536 instead ofa plenum as shown in FIGS. 1-7. A cooling flow 552 enters the airfoil520 through an aperture 554 located at a root 528 of the airfoil blade520. In the embodiment as illustrated, the cooling flow 552 locatedwithin the serpentine passageway 536 flows at a relatively highervelocity when compared the cooling flow in the plenum shown in FIGS.1-7. The coolant flow 552 flows within the vertical passages 537 of theserpentine passageway 536. A portion of the coolant flow 552 flowsthrough the serpentine passageway 536, and a remaining portion of thecoolant flow 552 flows from the serpentine passageway 536 and into theplurality of cooling passageways 542. The cooling passageways 542 extendaxially from the serpentine passageway 536 and terminate at a trailingedge 534 as a series of cooling holes 550, where the cooling flow 552exits the cooling holes 550. In the embodiment as shown in FIG. 8, thevelocity of the coolant flow 552 is high enough such that the effects ofthe Coriolis forces that act upon the coolant located in the coolingpassageways 542 are reduced when compared to the cooling passagewaysillustrated in FIGS. 1-7. The reduced Coriolis forces will in turnresult in increased heat transfer coefficients. Higher heat transfercoefficients tend to cool areas of high heat load while reducing theeffects of rotational forces in the cooling passageways 542.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. An airfoil, comprising: an airfoil blade having a trailing edge, apressure sidewall and a suction sidewall, a widest cross section of theairfoil blade defined between the suction sidewall and the pressuresidewall; a plenum located along the widest cross section; and at leastone passageway extending in an axial direction from the plenum andterminating at the trailing edge, the at least one passageway in fluidcommunication with and receiving a flow from the plenum.
 2. The airfoilof claim 1, wherein the airfoil blade includes a root and a tip portion,wherein a plurality of passageways are located between the root portionand the tip portion.
 3. The airfoil of claim 2, wherein the root iscoupled to a platform of the airfoil.
 4. The airfoil of claim 2,comprising at least one tip passageway that terminates at the tipportion of the airfoil blade.
 5. The airfoil of claim 1, wherein the atleast one passageway includes a generally curved profile.
 6. The airfoilof claim 1, comprising a plurality of passageways that have a staggeredconfiguration with respect to one another.
 7. The airfoil of claim 1,wherein the at least one passageway has a tapered configuration, whereina first diameter of the at least one passageway is measured at aproximate end of the at least one passageway with respect to the plenumand a second diameter is measured at a distal end of the at least onepassageway with respect to the plenum, wherein the first diameter isgreater than the second diameter.
 8. The airfoil of claim 1, wherein theat least one passageway includes a plurality of protrusions that createa turbulence in the flow located in the at least one passageway.
 9. Theairfoil of claim 1, wherein the at least one passageway is a pluralityof passageways, a portion of the plurality of passageways having astepped configuration where a first diameter of the portion of theplurality of passageways is measured at a proximate end of the pluralityof passageways with respect to a plenum, and a second diameter ismeasured at a distal end of the plurality of passageways with respect tothe plenum, wherein the first diameter is greater than the seconddiameter and the first diameter to the second diameter changes by a steplocated in the plurality of passageways.
 10. The airfoil of claim 9,wherein a remaining portion of the plurality of passageways have thefirst diameter being less than the second diameter.
 11. The airfoil ofclaim 1, wherein the at least one passageway is a plurality ofpassageways, wherein least one of the passageways is oriented to extenddiagonally and cross over another one of the passageways.
 12. Theairfoil of claim 1, wherein the plenum is located along a leading edgeof the airfoil.
 13. An airfoil, comprising: a platform; an airfoilblade, comprising: a leading edge, a trailing edge, a root and a tipportion, the root of the airfoil blade being coupled to the platform; aplenum located along the leading edge; and a plurality of passagewayslocated between the root portion and the tip portion, at least one ofthe plurality of passageways extending in an axial direction from theplenum and terminating at the trailing edge, and the plurality ofpassageways in fluid communication with and receiving a flow from theplenum.
 14. The airfoil of claim 13, comprising at least one tippassageway that terminates at the tip portion of the airfoil blade. 15.The airfoil of claim 13, wherein at least one of the plurality ofpassageways includes a generally curved profile.
 16. The airfoil ofclaim 13, wherein the plurality of passageways have a staggeredconfiguration with respect to one another.
 17. The airfoil of claim 13,wherein at least one of the plurality of passageways has a taperedconfiguration, wherein a first diameter of the at least one of theplurality of passageways is measured at a proximate end with respect tothe plenum and a second diameter is measured at a distal end withrespect to the plenum, wherein the first diameter is greater than thesecond diameter.
 18. The airfoil of claim 13, wherein the at least oneof the plurality of passageways includes a plurality of protrusions thatcreate a turbulence in the flow.
 19. The airfoil of claim 13, wherein aportion of the plurality of passageways have a stepped configurationwhere a first diameter of the portion of the plurality of passageways ismeasured at a proximate end with respect to a plenum, and a seconddiameter is measured at a distal end with respect to the plenum, whereinthe first diameter is greater than the second diameter and the firstdiameter to the second diameter changes by a step located in theplurality of passageways.
 20. An airfoil, comprising: a platform; anairfoil blade, comprising: a leading edge, a trailing edge, a root, anda tip portion, the root of the airfoil blade being coupled to theplatform; a serpentine passageway located along the leading edge; aplurality of passageways located between the root portion and the tipportion, at least one of the plurality of passageways extending in anaxial direction from the serpentine passageway and terminating at thetrailing edge, at least one of the plurality of passageways including agenerally curved profile, and the plurality of passageways in fluidcommunication with and receiving a flow from the serpentine passageway.